The conventional single-fueled boilers of the prior art usually operate on either oil, gas, wood or coal. Boilers operating on coal have often been replaced with more convenient, cleaner oil-fired boilers. Shortages of oil can, however, make coal more competitive in price, although there are air pollution problems associated with its use. Thus, a single-fueled boiler installation lacks the flexibility to cope with fluctuating supplies and prices. Furthermore, seasonal fluctuations in temperature may make one fuel preferable at one time of the year and another at another time. Because of these factors boilers which can simultaneously operate using two or more fuels have been developed. However, these multi-fueled boilers do not always operate at peak efficiency. It is difficult to construct a boiler which can burn two fuels, one solid and one liquid, with combustion efficiency. For example, ash from a solid combustion can interfere with operation of a gas or oil burner. Furthermore, air pollution problems are more complex when two fuels are burned at the same time, or at different times, in the same boiler.
It is an object of this invention to provide an improved multi-fueled boiler having increased efficiency of combustion.
It is also an object of this invention to provide an improved efficiency multi-fueled boiler using a solid fuel such as coal and a liquid fuel such as oil simultaneously or separately.
It is a further object of this invention to provide an improved multi-fueled boiler having a cooler, more completely burned flue gas effluent so as to decrease air-pollution.
It is also an object of this invention to provide a boiler which can conveniently operate simultaneously on or switch between fuels to provide improved economy and greater efficiency.
It is yet another object of this invention to provide a boiler which uses at least two fuels so as to provide more flexibility during shortages of a particular fuel.